How to make the highlight of the illuminating object penetrate another object?
The Translucent shader behaves similarly to the Subsurface Scattering shader in that it 'scatters' light through the surface - but does not take account of the direction of the incident light and so does not allow the light source to 'show through' as would happen with thin paper.

In order to produce such an effect you can use a Refraction shader with high roughness to allow a blurred projection of the inner lamp to show through.

For example, here's an example of a translucent surface made up of a Diffuse with added Translucency :



Note the cube inside the mesh producing the illumination (the cube is set to an emission material with a strength of 30).

By mixing in a Refraction shader we can allow a distorted image of the emissive cube to show through :

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The Mix shader can be adjusted to vary the strength of the 'show through'. Note also that the IOR of the Refraction shader can be adjusted to vary the 'blur' through the surface.

Note that I've omitted the Emission shader, relying instead on the emission from the light source within.